In connection with weight reduction of a vehicle, the use of aluminum material has become more prevalent, and accordingly, research has been undertaken regarding how to conjoin steel and aluminum materials. The two materials are difficult to conjoin together because of their material differences, and therefore a vehicle body is usually formed entirely of steel or of aluminum. To overcome this problem, generally by conjoining different materials such as steel and aluminum, electromagnetic forming has been proposed.
However, prior art conjoining schemes for steel and aluminum using electromagnetic forming of steel have only been applicable to the case in which an aluminum member is disposed exterior to a steel member. This is because a sufficient induced magnetic field is formed only at the aluminum. That is, the steel does not form a sufficient induced magnetic field, so the aluminum should be disposed exterior to the steel or the capability of a conjoining apparatus must be very high in order to enable conjoining of an exteriorly disposed steel member therewith.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.